Electricity: circuit makers and breakers – Special application – Change of inclination or of rate of motion responsive
Reexamination Certificate
2002-02-22
2003-10-21
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Special application
Change of inclination or of rate of motion responsive
C200S061520, C200S061530
Reexamination Certificate
active
06635835
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an acceleration detecting device of a passive safety system for driving and controlling a passive safety device of a vehicle.
2. Description of Related Art
A conventional acceleration detecting device will be described which is provided in a control unit (passive safety system) for controlling the operation of a passive safety device of a vehicle such as an air bag system or the like.
FIG. 11
is an illustration to show an example of a position where a control unit including a conventional acceleration detecting device and a passive safety device are disposed in a vehicle and to show a view when viewed from the top side of the vehicle. In
FIG. 11
, a reference character
110
denotes a control unit having the acceleration detecting device disposed in the center tunnel (not shown) of the vehicle. A reference character
111
denotes the passive safety device disposed in a steering wheel (not shown).
FIG. 12
is a side view to show a schematic configuration of the conventional acceleration detecting device. In
FIG. 12
, a reference character
100
denotes the acceleration detecting device. A reference character
101
denotes a mass body having a mass and a reference character
102
denotes a sliding shaft for slidably supporting the mass body
101
. A reference character
103
denotes an elastic body disposed in such a way as to surround the sliding shaft
102
. When the acceleration detecting device
100
is not operated, the mass body
101
is pressed onto one side by the elastic force of the elastic body
103
. A reference character
104
denotes movable contact points each formed in the shape of a spring and fixed to the top and bottom of the mass body
101
. A reference character
105
denotes fixed contact points fixed to the ceiling portion and bottom portion of a tunnel-shaped hole, made in the acceleration detecting device
100
, into which the mass body
101
goes when it slides on the sliding shaft
102
.
FIGS. 13A and 13B
are illustrations of the mass body
101
and the sliding shaft
102
constituting a part of the conventional acceleration detecting device
100
.
FIG. 13A
is a perspective view of the mass body and the sliding shaft in the ordinary state where the acceleration detecting device
100
is not operated and
FIG. 13B
is a cross-sectional view. In
FIG. 13
, a reference character
101
denotes the mass body. The mass body
101
is made of brass, for example, and has a predetermined mass. A reference character
101
a
denotes a through hole made through the mass body
101
. A reference character
102
denotes the sliding shaft passing through the through hole
101
a
and being fixed. The sliding shaft
102
is made of, for example, a PBT (polybutylenephthalate) resin or the like and is circular in cross section. The through hole
101
a
and the sliding shaft
102
are formed, for example, by a die molding method or the like. The circle of the cross section of the mass body
101
is larger than the circle of the cross section of the sliding shaft
102
, so the mass body
101
can slide on the sliding shaft
102
. A reference character Gz denotes a gravity component applied to the mass body
101
.
In the state where the acceleration detecting device
100
including the mass body
101
and the sliding shaft
102
is not operated (hereinafter referred to as an ordinary state), only the gravity Gz is applied to the mass body
101
and thus the upper portion of the mass body
101
is in contact at one point with the upper portion of the sliding shaft
102
.
Next, the operation of the acceleration detecting device
100
will be described.
In the case where a vehicle collides with an object in front of the vehicle and receives an impact (deceleration), the mass body
101
receives an inertial force from the impact. In the case of a large impact, the inertial force overcomes the elastic force of the elastic body
103
to slide the mass body
101
on the sliding shaft
102
to put the mass body
101
into the tunnel-shaped hole. When the mass body
101
moves a distance larger than a predetermined distance, the movable contact points
104
come in contact with the fixed contact points
105
to bring these two contact points into electric conduction.
The acceleration detecting device
100
is a mechanical type device and the control unit
110
has double circuits of the acceleration detecting device
100
and an electromechanical acceleration detecting device (semiconductor acceleration sensor). Only after both the circuits output a signal to operate the passive safety device
111
, the passive safety device
111
is operated. The circuits for operating the passive safety device
111
will be described in the following.
FIG. 14
is a circuit diagram to show an electric configuration of the control unit
110
provided with the conventional acceleration detecting device
100
and the passive safety device
111
. In
FIG. 14
, a reference character
112
denotes a power source. A reference character
113
denotes a semiconductor-type acceleration sensor having a function of detecting an impact acceleration applied to the vehicle. A reference character
114
denotes a microcomputer having a function of processing a signal from the semiconductor-type acceleration sensor
113
. A reference character
115
denotes a semiconductor switch for opening or closing a driving circuit of the passive safety device
111
.
The control unit
110
is constituted by the power source
112
, the semiconductor-type acceleration sensor
113
, the microcomputer
114
, the semiconductor switch
115
and the mechanical acceleration detecting device
100
. Further, the passive safety device
111
is constituted by the driving circuit, opened or closed by the semiconductor switch
115
, and the safety device body.
Next, the operation of the circuit of the control unit
110
and the passive safety device
111
will be described.
For example, in the case where a vehicle collides head-on with an object, the semiconductor-type acceleration sensor
113
disposed in the control unit
110
detects an impact acceleration and outputs a detected acceleration signal to the microcomputer
114
. The microcomputer
114
converts the signal from the semiconductor-type acceleration sensor
113
into digital data by means of an internal A/D converter and performs a predetermined processing to close the semiconductor switch
115
if the impact is larger than a predetermined value.
Further, similarly, in the mechanical acceleration detecting device
100
disposed in the control unit
110
, in the case where an impact larger than a predetermined value is applied to the vehicle, as described above, the internal contact points are brought into conduction to close the circuit.
In this manner, when the vehicle receives the impact larger than the predetermined value, both circuits of the semiconductor switch
115
and the mechanical acceleration detecting device
100
are closed to pass a current through the driving circuit of the passive safety device
111
, thereby operating the passive safety device
111
.
The acceleration detecting device in the conventional passive safety device of the vehicle is constituted in this manner and performs the predetermined operation. However, since both of the mass body
101
and the sliding shaft
102
are circular in cross section, the movement of the mass body
101
becomes unstable, depending on the direction of collision of the vehicle, and when the mass body
101
slides on the sliding shaft
102
, the mass body
101
rattles. In this case, there is presented a problem that the timing of operation of the passive safety device might be delayed.
The problem will be described in detail in the following.
In the case where the vehicle collides head-on with the object, the direction of impact applied to the mass body
101
agrees with the direction of detecting an acceleration, that is, the axial direction of the sliding shaft
102
. For this reason, the mass body
101
can stably slide on the
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